Syntheses of Heterocycles Utilizing Trimethylsilyldiazomethane

点击翻译按钮获取中文摘要

Synthesis of heterocycles utilizing trimethylsilyldiazomethane (TMSCHN_2) , a useful reagent for generating alkylidene carbenes from carbonyl compounds, was investigated as follows :1. Lithium trimethylsilyldiazomethane (TMSC(Li)N_2), easily prepared from TMSCHN_2 with n-BuLi or LDA,smoothly reacted with N,N-dialkylamides of alpha-keto acids and N,N-disubstituted alpha-amino ketones to give 2-oxo-3-pyrrolines (C-H insertion products) and 3-pyrrolines (C-H insertion products) in good yields via alkylidene carbene intermediates, respectively.2. TMSC (Li) N_2 easily reacted with beta-amino ketones to give 2-pyrrolines (N-H insertion products) in good yields, which easily underwent oxidation by treatment with manganese dioxide (CMD,chemical manganese dioxide) to afford the corresponding pyrroles.3. TMSC (Li) N_2 smoothly reacted with o-siloxybenzaldehydes and o-siloxyacetophenones to give the corresponding o-siloxyphenylacetylenes via alkylidene carbene intermediates, which afforded benzofurans in good yields by treatment with tetrabutylammonium fluoride. Furthermore, 3-benzofuranmethanols could be obtained when the reaction was performed in the presence of electrophiles such as aromatic and heteroaromatic aldehydes.